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authorSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>2014-03-10 21:39:20 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-03-20 13:43:44 +0100
commit4b0b68af37b930403cf9074c0cf504fc2387c2fa (patch)
treeb0970ac5f825cab0751695c5355c78a91d2a48a4 /arch/arm64/kernel
parentarm64, hw_breakpoint.c: Fix CPU hotplug callback registration (diff)
downloadlinux-4b0b68af37b930403cf9074c0cf504fc2387c2fa.tar.xz
linux-4b0b68af37b930403cf9074c0cf504fc2387c2fa.zip
arm64, debug-monitors: Fix CPU hotplug callback registration
Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the debug-monitors code in arm64 by using this latter form of callback registration. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Ingo Molnar <mingo@kernel.org> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'arch/arm64/kernel')
-rw-r--r--arch/arm64/kernel/debug-monitors.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 636ba8b6240b..c9855313eb27 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -155,12 +155,16 @@ static struct notifier_block os_lock_nb = {
static int debug_monitors_init(void)
{
+ cpu_notifier_register_begin();
+
/* Clear the OS lock. */
smp_call_function(clear_os_lock, NULL, 1);
clear_os_lock(NULL);
/* Register hotplug handler. */
- register_cpu_notifier(&os_lock_nb);
+ __register_cpu_notifier(&os_lock_nb);
+
+ cpu_notifier_register_done();
return 0;
}
postcore_initcall(debug_monitors_init);